1. This invention relates to the general field of power shifted transmissions and electronic controls therefor.
2. Prior Art
It has been known in the prior art to use hydraulic control valves for the control of power shifted transmissions, and further to use various orifices and shuttling valves to control pressure buildup in the friction elements for the transmission to provide for gradual or rapid pressure buildup depending upon conditions and as indicated by movement of a control valve. Further it has been known to provide for electrically operated control valves such as solenoid valves with off/on positions which will operate to supply fluid pressure to the power shifted clutches and to use various accumulator devices to cushion the engagement of said clutches. The important control feature which has been long desired is to have a torque control over the power shifted clutches, such that the system will automatically provide for engagement of the clutch to change ratio, limiting the torque through the clutch to prevent jerky operation of the vehicle and also prevent skidding the wheels of the vehicle and creating an inefficient system, and likewise prevent having such a long delay in the shift that the clutch is damaged. It is further desirable that an input be made into the electronic control or other control whereby maximum torque to be developed is set to match the control function to the general conditions under which the vehicle is operating. Obviously, for example, a high torque level is not to be maintained during a shift in an off road or other type vehicle when extremely slippery conditions are present since continuous spinning of the wheels would result.